1. Field of the Invention
The present invention relates generally to test apparatuses for early landslide detection and, more particularly, to a test apparatus for early landslide detection fully-connected with pore water pressure, surface displacement and shear surface, which calculates a factor of safety of a slope based on variation in pore water pressure, surface displacement and shear surface of a soil mass constituting landslide materials and predicts a change in factor of safety depending on small deformation of the ground, thus making early landslide detection possible.
2. Description of the Related Art
Generally, landslides refer to a collapse of slopes and are caused by various reasons, for example, torrential rainfall, earthquakes, snow melting, etc. In areas where there are many mountains because of geomorphological characteristics, areas where mountains or hills are cut for constructing roads or the like, or areas where landslide risk evaluation is necessary due to construction of dams, banks or the like, determining the stability of slopes is required. Furthermore, in areas where landslide occurrence frequency is relatively high, early detection of movement indicating a landslide is imminent and setting up disaster prevention measures are required. Landslides mainly occur because of earthquakes or localized heavy rain in summer. Such a landslide is a phenomenon in which in a slope having a slip plane (a failure plane) a soil mass above the slip plane is deformed. When the sum of shear forces on the slip plane is greater than the sum of resistance forces, a landslide is caused. When the slope collapses, the failure slope leads to a debris flow having different magnitudes depending on rainfall conditions and geomorphological conditions, and may result in property damage and/or loss of life.
To evaluate the stability of a slope, the factor of safety of the slope must be determined. The factor of safety is the ratio of shear strength to shear stress that is present at time of failure, that is, at a time when shear strength to shear stress reaches an equilibrium limit. In other words, the factor of safety is expressed as shear strength/shear stress. Typically, if the factor of safety is less than 1, the slope is analyzed as being unstable. However, although the factor of safety of the slope is suitable for determining whether the slope is stable or not, it is not easy to predict a failure time of the slope because the resultant force of the shear strength on the failure plane of the slope continuously varies. Thus, a test apparatus for early landslide detection, which can determine shear strength taking displacement of the ground surface where a slope is deformed and a pore water pressure of a failure plane into account and the degree of particle breakage on a shear surface, is required.
Meanwhile, a conventional technique pertaining to the present invention was proposed in Korean Patent Unexamined Publication No. 10-2012-0073406, entitled “Landslide calibration chamber test apparatus using artificial rainfall simulator.” The apparatus according to this conventional technique includes a chamber which creates a slope, an artificial rainfall simulator which sprays artificial rain water onto the slope of the chamber, and an instrument device which measures the behavior of the slope.
In this conventional apparatus, debris flow materials are arranged in the longitudinal direction of the chamber, thus forming a slope. While the artificial rainfall simulator sprays artificial rain water, the behavior of the slope is measured.
However, the conventional apparatus varies only a supply rate of water using the artificial rainfall simulator but cannot provide the shear surface environment of the debris flow materials nor simulate surface displacement. Therefore, the conventional apparatus cannot calculate variation in factor of safety depending on the surface displacement and soil mass deformation.